HSC Survey Results

German Bank Survey # 5 Results from 27/09/2023

Survey Details

9 commercial purse seiners conducted this fishing survey on 27/09/2023 starting at 20:00:00.

All vessels ran two transects in the German Bank box and one transect in the Seal Island Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Melissa.

A total of 159 tags were applied during the survey over 1 event(s) from 2023-09-18 to 2023-09-18 from 1 vessel(s).

Samples were obtained for target strength estimation.

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for German Bank using standardized parallel transects is 15,242mt, and with turnover applied 11,360mt. The preliminary biomass estimate for Seal Island is 53,844mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
BP T01 2023-09-28 00:51:47 2023-09-28 03:17:57 -66.434 43.564 -66.434 43.234 GB 36.80 8.16
BP T02 2023-09-28 03:54:55 2023-09-28 06:21:50 -66.300 43.235 -66.299 43.566 GB 36.77 8.11
C1 T01 2023-09-28 00:00:10 2023-09-28 02:25:16 -66.494 43.566 -66.492 43.235 GB 40.30 9.00
C1 T02 2023-09-28 02:58:42 2023-09-28 05:26:59 -66.356 43.234 -66.358 43.570 GB 39.33 8.59
FM T01 2023-09-28 00:54:58 2023-09-28 03:24:21 -66.474 43.565 -66.474 43.232 GB 38.49 8.35
FM T02 2023-09-28 04:00:29 2023-09-28 06:26:03 -66.338 43.236 -66.337 43.568 GB 37.83 8.42
LB T01 2023-09-27 23:49:59 2023-09-28 02:28:54 -66.454 43.565 -66.454 43.234 GB 38.15 7.78
LB T02 2023-09-28 03:10:48 2023-09-28 05:43:58 -66.318 43.234 -66.318 43.567 GB 37.97 8.03
LJ T01 2023-09-27 23:53:23 2023-09-28 02:23:17 -66.396 43.567 -66.396 43.233 GB 37.12 8.02
LJ T02 2023-09-28 03:02:34 2023-09-28 05:32:57 -66.259 43.233 -66.259 43.569 GB 37.33 8.04
LM T01 2023-09-27 23:44:00 2023-09-28 02:10:12 -66.377 43.565 -66.377 43.233 GB 37.67 8.35
LM T02 2023-09-28 02:47:20 2023-09-28 05:14:37 -66.240 43.232 -66.239 43.567 GB 37.78 8.31
MS T01 2023-09-28 00:04:26 2023-09-28 02:36:49 -66.415 43.553 -66.415 43.235 GB 38.87 8.26
MS T02 2023-09-28 03:19:14 2023-09-28 05:47:14 -66.278 43.234 -66.279 43.564 GB 38.61 8.45
SL T01 2023-09-28 00:52:33 2023-09-28 02:45:24 -66.126 43.501 -66.125 43.248 GB 30.10 8.64
SL T02 2023-09-28 02:55:40 2023-09-28 04:49:14 -66.166 43.247 -66.167 43.502 GB 30.04 8.57
SL T03 2023-09-28 05:01:09 2023-09-28 06:54:27 -66.209 43.502 -66.210 43.247 GB 30.54 8.73
TM T01 2023-09-27 23:43:20 2023-09-28 01:56:04 -66.146 43.506 -66.147 43.246 GB 28.92 7.06
TM T02 2023-09-28 02:06:40 2023-09-28 04:03:47 -66.187 43.248 -66.188 43.502 GB 28.32 7.83
TM T03 2023-09-28 04:17:47 2023-09-28 06:09:50 -66.229 43.503 -66.231 43.246 GB 28.61 8.27

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
TM T02 -35.5 -36.296 0.833
SL T02 -35.5 -40.190 0.340
C1 T01 -35.5 -47.772 0.059
C1 T02 -35.5 -50.839 0.029
FM T01 -35.5 -52.194 0.021
FM T02 -35.5 -52.359 0.021
LM T01 -35.5 -52.583 0.020
TM T01 -35.5 -53.195 0.017
MS T01 -35.5 -53.375 0.016
BP T02 -35.5 -53.982 0.014
LJ T01 -35.5 -54.005 0.014
LB T02 -35.5 -54.074 0.014
BP T01 -35.5 -54.421 0.013
LB T01 -35.5 -54.692 0.012
MS T02 -35.5 -54.733 0.012
SL T01 -35.5 -54.912 0.011
LJ T02 -35.5 -55.597 0.010
LM T02 -35.5 -55.673 0.010
SL T03 -35.5 -56.655 0.008
TM T03 -35.5 -60.308 0.003
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
German Bank -35.5 796 -52.6788 0.0189 15,241.68 NA NA 2,719.85 17.84
Seal Island -35.5 272 -42.5343 0.2019 53,843.74 NA NA 37,303.41 69.28
School Survey NA NA NA NA NA NA NA NA NA

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by TM, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by TM, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
German Bank 1 2023-08-06 2,686.514 NA 2022-08-14 16,285 16,285 22,081 22,081
German Bank 2 2023-08-20 4,930.454 4,406.486 2022-08-28 7,472 4,296 11,699 7,393
German Bank 3 2023-09-03 9,959.441 8,901.000 2022-09-11 12,507 10,464 11,902 8,826
German Bank 4 2023-09-13 16,265.846 13,203.000 2022-09-25 15,924 13,216 12,503 9,761
Seal Island 1 2023-08-06 1,205.361 NA 2022-08-14 2,598 2,598 2,086 2,086
Seal Island 2 2023-08-20 1,917.847 NA 2022-08-28 1,048 1,048 570 570
Seal Island 3 2023-09-03 2,062.584 NA 2022-09-11 6,941 6,941 6,392 6,392
Seal Island 4 2023-09-13 5,635.715 NA 2022-09-25 4,634 4,634 3,732 3,732
German Bank 5 2023-09-27 15,241.681 11,360.000 2022-10-10 19,539 16,337 20,247 17,675
Seal Island 5 2023-09-27 53,843.744 NA 2022-10-10 5,243 5,243 5,604 5,604
German Bank 6 NA NA NA 2022-10-23 13,399 8,684 15,565 10,823
Seal Island 6 NA NA NA 2022-10-23 2,944 2,944 3,260 3,260
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2022 German Bank 85,126.00 69,282 93,997 76,559
2022 Seal Island 23,408.00 23,408 21,644 21,644
2023 German Bank 49,083.94 NA NA NA
2023 Seal Island 64,665.25 NA NA NA

Tagging, Plankton, and CTD Data

Tag Data

Vessel Tags
Lady Melissa 159

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Melissa Lady Melissa
Set Number GB2023-09 GB2023-10
Ground GB GB
Date 27/09/2023 27/09/2023
Wind Direction (km/h) N N
Swell (m) 0.5 0.5
Air Temp (c) 13 13
Tow Details
Tow Start 19:03:00 19:19:00
Tow End 19:13:00 19:29:00
Start Lat 43.57194 43.56300
End Lat 43.5585 43.5810
Start Lon -66.35317 -66.36583
End Lon -66.35617 -66.36483
Avg Tow Depth (m) NA NA
Speed 4.7 6.7
Heading 180 0
Tide Direction against with
Other Data Collection
Flow Start 438682 485146
Flow End 485146 531610
No. Revolutions 46464 46464
Distance (m) 1248.627 1248.627
Volume 3922.562 3922.562
Secchi Disappear (m) 7 7
Secchi Reappear (m) 6 6

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is GB2023-09, which was against the tide and had an average depth of NAm. The second tow is GB2023-10, which was with the tide and had an average depth of NAm.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2023 German Bank surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for German Bank.

Vessel Performance

Speed

Average vessel speed was 8.26. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

Distance

No significant distance was cut from the planned lines; vessels covered the planned area well.